1) Field of the Invention
The present invention relates to the forming of members and, more particularly, an apparatus and method for forming corrugated contours in a member, such as a metal web that is disposed between flanges to produce a stringer or beam.
2) Description of Related Art
Corrugated members are widely used for a variety of applications. For example, metal structural panels used in vehicles, buildings, and containers can be corrugated to provide an increased resistance to bending or buckling relative to flat sheets. A corrugated web can be used to form a structural component such as a beam or stringer. For example, a corrugated stringer, which includes a corrugated web that extends between top and bottom flanges, can be used in the construction of a larger assembly such as an aircraft wing or fuselage. The profile of such a corrugated member typically defines wave-like sinusoidal contours, which affect the rigidity and other structural characteristics of the member. Relative to a stringer with a planar web, the corrugated stringer can generally provide greater rigidity, greater strength, and/or decreased weight.
According to one conventional method of forming a corrugated stringer, the web is pre-corrugated by conventional forming methods and then welded to the flanges. The web typically is characterized by some “spring back.” That is, if the web is elastically and plastically deformed from a flat configuration to the corrugated configuration, the web may then return partially from its formed shape when the forming forces are removed. In addition, the amount of spring back can vary throughout the web and throughout different webs, e.g., depending on variations in the web thickness or other properties. When the pre-corrugated web is welded to the flanges, any spring back in the web can result in the web having a configuration that differs from the desired configuration. In some cases, the amount of expected spring back can be calculated or otherwise determined so that the web can be formed to a shape that, after spring back, conforms to the desired configuration. However, an accurate determination of spring back can be difficult or impossible and can add to the cost and complexity of the manufacturing process. Thus, in some cases, the web may not be lined up and welded with the flanges in the desired configuration, and the desired configuration of the stringer may not be achieved.
The manufacturing operation of such corrugated stringers can be further complicated by the use of materials with special forming or processing requirements and characteristics. For example, welding of some materials such as titanium generally requires a controlled environment to prevent undesired oxidation or other chemical effects to the material during welding. For this reason, titanium is often welded in a vacuum chamber. That is, titanium components are arranged in a vacuum chamber, the chamber is closed, air is evacuated from the chamber, and then the welding operation is performed. This evacuation method increases the time and expense for welding.
Thus, there exists a need for an improved apparatus and method for forming corrugated contours in a member and for welding members, e.g., for the manufacture of corrugated stringers or beams and the like.